20"W X 8"H [Duct Opening] Steel Air Vent Return Grille - HVAC VENT DUCT COVER DIFFUSER - [Outer Dimensions: 21.75"W X 9.75"H] 18" Round Duct Pipe + Product Details Size - 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size - 20"w X 10"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 23

+ Product Details Size - 18"w X 16"h is the size for the duct opening measurement only

+ Product Details Size - 12"w X 20"h is the size for the duct opening measurement only

+ Product Details Size - 20"w X 16"h is the size for the duct opening measurement only

20"W X 8"H [Duct Opening] Steel Air Vent Return Grille HVAC VENT DUCT COVER DIFFUSER [Outer Dimensions: 21.75"W X 9.75"H] 18" Round Duct Pipe + Product Details Size 4 X 12 Is CRFG2028 Width_14in + Product Details Size 20"w X 10"h is the size for the duct opening measurement only actual front end outer dimensions are approximately 23